ARQUES, France — The furnace, heated to 1,500 degrees Celsius, was glowing red. Workers at the Arc International glass factory loaded it with sand that slowly pooled into a molten mass. Nearby on the factory floor, machines transformed the shapeless liquid with a blast of hot air into thousands of delicate wineglasses, destined for sale to restaurants and homes worldwide.
Nicholas Hodler, the CEO, surveyed the assembly line, shimmering blue with natural gas flames. For years, Arc had been powered by cheap energy that helped turn the company into the world’s largest producer of glass tableware — and a vital employer in this working-class region of northern France.